(Deficit) Equity - Private Placement (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended	3 Months Ended			12 Months Ended
	Jun. 09, 2016	May 23, 2016	Mar. 29, 2016	Nov. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Units issued in connection with private placement (in units)									5,402,985
Consideration for units issued in connection with private placement								$ 20.0	$ 5.8	$ 9.8
Aggregate percentage of interest									200.00%
Common Units
Class of Stock [Line Items]
Units issued in connection with private placement (in units)				1,000,000,000.00	5,200,000
Net proceeds from private equity placement					$ 139.8
Gross proceed issuance of private placement offering					$ 140.2
Common units per share (in units per share)					$ 26.96
Placement fees					$ 0.4
General Partner
Class of Stock [Line Items]
Units issued in connection with private placement (in units)					106,122	1,938	15,307		108,060
Consideration for units issued in connection with private placement	$ 1.1		$ 8.2		$ 2.9		$ 0.5
May 2016 Acquisition
Class of Stock [Line Items]
Consideration for units issued in connection with private placement		$ 7.1
Shell Pipeline Company L P | Common Units
Class of Stock [Line Items]
Units issued in connection with private placement (in units)									0
Shell Pipeline Company L P | May 2016 Acquisition | General Partner
Class of Stock [Line Items]
Aggregate percentage of interest								2.00%